Such an active stabilisation system for damping a ship's motion is known, for example from NL patent No. 1023921. In said patent specification it is proposed to configure a stabilisation element that projects into the water from the ship's hull below the water line as a cylindrical stabilisation element. This cylindrical stabilisation element is rotated about its longitudinal axis so as to compensate for the roll of the ship while it is stationary. To that end, the ship is fitted with sensor means, for example angle sensors, speed sensors and acceleration sensors, by means of which the angle, the rate or the acceleration of the ship's roll are sensed. Control signals are generated on the basis of the data being obtained, which signals control the rotation of the rotatable stabilisation element as regards the direction of rotation and the speed of rotation and also the movement of the stabilisation element relative to the ship.
Under the influence of the rotational movement of the stabilisation element and the water flowing past as a result of the stabilisation element moving relative to the stationary ship, a correction force is generated perpendicular to the direction of rotation and the direction of movement. This physical phenomenon is also referred to as the Magnus effect, on the basis of which the correction force is used for opposing the ship's roll. This Magnus effect-based stabilisation system comprising rotating cylindrical stabilisation elements provides a very large correction force already at very low sailing speeds, which force is used as a lifting force for opposing the roll.
This is an ideal solution in the case of ships sailing at low speeds of around 3-4 knots. The stabilisation system is primarily used with stationary ships, however, wherein the rotating stabilisation elements move in a reciprocating translational fashion relative to the ship's hull, and wherein use is made of the relative velocity of the water that flows past the translating stabilisation elements for realising the correcting Magnus effect.
A drawback of the stabilisation system described in said patent is that a reciprocating translational movement relative to the ship's hull is imparted to the stabilisation elements by the moving means. This means that the moving means constantly need to be changed over for accelerating and decelerating the mass of the rotating stabilisation element in one direction of translation and accelerating and decelerating the mass of the rotating stabilisation element in the other, opposite direction of translation. The mass inertia of the system further has an adverse effect on the smooth functioning of the system because also the direction of rotation of the stabilisation elements must be reversed each time by actuating the driving means.
This mass acceleration-deceleration makes considerable demands on the energy sources aboard the ship in question. The generators of the moving means or driving means are loaded heavily and, because of the required change-overs, in a constantly varying manner. This variation is offset as much as possible by using accumulators (in the case of hydraulic drive) for smoothing the peak currents.